Storage tube



Aug. 30, 1966 D. R. CHARLES STORAGE TUBE 2 Sheets-Sheet 1 Filed May 16, 1965 Aug. 30, 1966 D. R. CHARLES STORAGE TUBE 2 Sheets-Sheet 2 Filed May 16, 1963 ATTOR United States Patent 3,270,242 STORAGE TUBE Daniel R. Charles, Paris, France, assignor to CSF-Cornpagnie Generale de Telegraphic Sans Fil, Paris, France Filed May 16, 1963, Ser. No. 280,819 Claims priority, application France, June 7, 1962,

8 Claims. (Cl. 315- The present invention relates to electron discharge devices of storage tube type, and more particularly to tubes comprising a grid covered with an insulation flooded by a slow and uniform beam of electrons emitted by a so-called flood gun, and, on the same side of the grid as this gun, a source of signal-carrying electrons, of which the velocity is just sufficient so that a deposit of positive charges is possible on the insulation of the grid, this source being either a so called writing gun, which is provided with usual control devices for the intensity and deflection of the electron beam, or a photoelectric cathode.

Direct view storage tubes known in the prior art comprise a fluorescent screen behind the grid covered with insulation. In this manner, at the places where positive charges have been deposited on the insulation by the writing beam, the electrons of the flood gun, which traverse the grid without erasing these charges and which are thereupon accelerated, come to impinge upon this screen thereby rendering visible the trace inscribed by the signalcarrying electrons, the visibility being maintained during the duration of remanence of the screen. This arrangement permits the observation during several seconds of very brief and very rapid phenomena; nevertheless, it presents the defect that it is not readily possible to transport or transmit at distance the image observed on the fluorescent screen, other than by the intermediary of a picture-taking optical system.

The present invention has for its object a tube exempt of this inconvenience, that is, which permits a transmis sion or transport at distance, in an extremely easy manner, of the output image with preservation of its qualities of brilliance and remanence.

Within the tube according to the present invention, one no longer obtains the output image in the optical form but in the form of electric signal that may be transmitted in a suitable manner and converted into an optical image at the place of arrival.

The tube according to the present invention which comprises all of the essential elements of a direct view storage tube except the fluorescent screen, is characterized by the presence of a target with induced conductivity, known per =se, this target being explored on the opposite face thereof by the electrons of the so-called reading gun, means being provided to collect the output signal produced by this exploration in a manner already known in storage analyzer tubes.

Accordingly, it is an object of the present invention to provide an electron discharge device of the storage tube type which eliminates in a highly effective manner the aforementioned shortcomings encountered with the prior art constructions.

It is another object of the present invention to provide an electron discharge device of storage tube type in which, in lieu of an optical image, electrical output signals are produced that are suitable for long-distance transmission with reproduction of the optical image remote therefrom and under preservation of the signal remanence.

A further object of the present invention resides in the provision of a storage tube electron discharge device which utilizes a target with induced conductivity to produce electrical output signals representative of the inscribed signals.

3,270,242 Patented August 30, 1966 "ice Still another object of the present invention resides in the provision of an electron discharge device of the storage type tube in which several superposed signals may be utilized to produce the image thereof for purposes of studying recurring phenomena, correlation problems, etc.

These and other objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawing which shows, for purposes of illustration only, several embodiments in accordance with the present invention, and wherein:

FIGURE 1 is a longitudinal cross sectional view through a first embodiment of an electron discharge device of the storage tube type in accordance with the present invention provided with a writing gun,

FIGURES 2 and 3 are enlarged partial views indicating certain details of the tube of FIGURE 1;

FIGURE 4 is a schematic diagram showing a modified construction for the output connection from the tube in accordance with the present invention, and

FIGURE 5 is a longitudinal cross sectional view through a modified embodiment of an electron discharge device in accordance with the present invention in which the signal-carrying electron source is a photoelectric cathode.

Referring now to the drawing wherein like reference numerals are used throughout the various views to designate like parts, and more particularly to FIGURE 1, one finds in the left portion of the tube illustrated therein, within the evacuated envelope 1 thereof, the usual elements of en electron discharge device of storage tube type, namely:

A first so-called writing gun, comprising a cathode 2, a Wehnelt electrode 3, accelerating and focusing anodes 4, 5 and 6, deflection plates 7 and 8 in two orthogonal planes, though it is understood that the present invention is not limited to the illustrated electrostatic deflection. This gun is fed by way of pins 9, the cathode 2 being carried, for example, at l850 v., the anodes 4 and '6 at +50 v. to +150 v. and the anode 5 at 1300 v. with respect to ground. This beam receives the modulation by a signal applied across the capacitor 43, connected to the terminal of a resistance 44 which is interconnected between the pin 9 and the supply terminal 45';

A second so-called flooding gun, comprising a cathode 10, a Wehnelt electrode 11 and an anode 12 provided in the center thereof with an orifice 13 for the passage of the flooding beam, and outside of the center thereof with an orifice 14 in the axis of the writing beam to permit passage to the latter. This gun is fed by way of pins 15, while the cathode is set, for example, at ground potential and the anode 12 is carried, for example, at a potential between +50 v. and +150 v. in common with the anodes 4 and 6;

An electrode 16 of truncated conical shape carried, for example, at +50 v. and .a cylindrical electrode 17 carried, for example, at v., these electrodes having for purpose the appropriate action on the slow beam emitted by the flooding gun in order to cause the same initially to diverge and thereupon orient substantially all of therays parallel to the axis of the tube as indicated at 18; they substantially do not act on the writing beam which is much faster;

A collector grid 19 carried, for example, at +210 v., this voltage being, with respect to the potential of the cathode 10, a slow-speed accelerating voltage, and with respect to the potential of the cathode 2 a relatively fastspeed accelerating voltage, just sufficient in order that the electrons of the Writing beam may traverse the grid 19 and reach the grid 20;

A storage grid 20, covered with :a layer of insulating, that is dielectric, material such as magnesium fluoride on the side of the guns, as at 21 and shown in the enlarged 3 view of FIGURE 2; the metal of this grid may be carried, for example, at +6 v., whereas the potential at the surface of the dielectric is fixed by the proximity of the grid 19.

To the right of the grid and in contrast to the known direct viewing tubes, the tube according to the present invention comprises a target with induced conductivity 22 constituted, as known in the art, by a metallic grid 23 (FIGURE 3) supporting a very thin layer, about 0.03 to 0.1 micron, of a metal such as aluminum 24, covered by an insulation layer 25, selected from the materials having the property of becoming momentarily conductors when they are penetrated by fast electrons, for example, Zinc sulfide, and also very thin, about 0.5 micron.

It is understood, however, that any other suitable material, either an insulating or a semi-conductor material in part or in full, could be utilized in the target in accordance with the present invention depending on the requirements thereof. This target is mounted on a support 26 which is fixed onto a ring 27 incorporated within the wall of the tube and carried at the high voltage of +8 kv. to 10 kv., applied at the terminal 42.

Near the insulating face of the target 22 is disposed a hollow cylinder 28, forming a collector of which the output across the passage 29 is connected on the one hand to a resistance 30 to which is applied, by way of terminal 31, a voltage equal to that of the target increased by an adjustable biasing voltage Vc equal to some tens. of positive volts, and on the other hand, to a condenser 32 across which one takes off the output signal at 33.

Between the collector 28 and the target 22 is disposed, in accordance with well known techniques, an annular member 34 forming a spot corrector of which the output across the passage 35 receives an adjustable voltage V for example, between -l5 v. and +15 v. with respect to the voltage applied to the collector 28.

A reading system is disposed on the side of the insulating face of the target which is composed: of a third electron gun, of a so-called reading gun, of conventional construction, comprising a cathode 36 and an anode 37, and which may additionally comprise all of the necessary focusing and control electrodes, not illustrated herein in detail; and of a sweep system, for example, an electrostatic sweep system comprising two pairs of deflection plates 38 and 39; conventional means (not illustrated) being provided to apply to these plates appropriate sweep voltages.

The base 40, on which are arranged the feed pins for the reading system, comprises among others a pin 41 connected to the cathode 36, and to which is applied a negative voltage VI of the order of 1.5 v. to 2 kv. with respect to the target 22. Since the anode 37 is placed at the potential near that of the target, a positive difference of potential substantially equal to that voltage is established between the anode 37 and the cathode 36. The feed connections for the other electrodes of the gun by way of the other pins of the base have not been shown in the drawing since they are conventional and may utilize all the known voltage values necessary to that effect.

Operation The tube described so far operates as follows:

In the absence of the signal, the insulating face 25 of the target 22 is swept by the beam issued from the cathode 36, accelerated by the anode 37 and deflected by the plates '38 and 39. For example, the accelerating voltage of the.

anode 37, of the order of 1.5 kv. to 2 kv., is such that the electrons are fast, that is, they produce, at the impact on the target, an emission of several secondary elec- .the secondary electrons move in the direction toward the collector 28. To the extent that the potential of the insulating face gradually increases, certain secondary electrons no longer move toward the collector, but fall back on the target. The quantity thereof, captured by the collector, therefore decreases progressively whereas the quantity that falls back on the target increases with the positive potential of the insulating face, thereby opposing the increase of positive charge of the target. Finally, after a certain number of sweeps, a state of equilibrium is established in which a certain constant current flows through the output 29 of the collector 28 but produces no signal at the connection 33 blocked by the condenser 32 whereas the insulating face 25 of the target 22 assumes uniformly a certain constant positive potential. The target then acts like a charged condenser.

If, on the other hand, the flooding beam is started, the electrons thereof which follow the paths indicated at 18, flood the entire surface of the grid 20, and since they are slow, they produce at the impact on this grid less secondary electrons that leave the grid than the quantity of primary electrons penetrating thesame. The insulating face 21 of the grid 20, therefore, becomes charged negatively and repulses the slow beam of which the electrons cannot traverse this grid.

If now a beam of relatively fast electrons, modulated by the signal, is emitted by the writing gun and deflected by the plates 7 and 8, then the insulating face 21 is swept and positive charges are created therein by the phenomenon analogous to the charge of the insulating layer 25. These positive charges form a charge pattern in accordance with the variations of the signal and compensate more or less the negative charges deposited by the slow beam. The electrons of the latter may now pass in larger or smaller quantities through the grid 20, are accelerated by the high voltage of the target 22 and bombard the same while traversing readily the metallic layer 24 and thereupon entering the insulating layer 25 which they traverse more or less completely. Along their paths within the insulation, these electrons liberate a large quantity of secondary electrons which nevertheless cannot escape to the outside as the speed thereof is relatively too low to permit them to traverse a solid medium. The path of each primary electron is therefore blazed by the secondary electrons liberated but remaining on the inside of the dielectric. The dielectric, therefore, becomes momentarily a conductor which constitutes the known phenomenon of induced conductivity.

By decomposing the condenser formed by the target into elementary condensers corresponding to each point of the charge pattern, one sees that each elementary condenser is discharged owing to the induced conductivity.

Additionally, this conductivity is proportional to the number of writing electrons which bombard the condenser plate of each elementary condenser, that is, to the intensity of the signal at the corresponding point. Everything therefore takes place as if each elementary condenser were more or less discharged across a variable resistance with the corresponding signal intensity. Since the potential of the metallic face of the target is fixed, there follows, at each point of the insulating face, a lowering of potential with respect to the positive potential inscribed by the reading beam, this lowering being a direct function of the intensity of the signal at the moment the corresponding point is swept.

A charge pattern of potential constituting the replica of the charge pattern formed previously on the grid 20 is therefore formed on the insulating face 25 of the target 22.

The continuation of. the sweeping operation of the insulating face by the reading beam produces the reestablishment of the initial positive potential, with emission toward the collector 28 of a quantity of secondary electrons that is more or less large depending on the swept charge pattern.

One introduces thus into the collector current variations which are transmitted by the condenser 32 and which constitute the useful signal at the output 33.

The purpose of the corrector ring 34 is, as is known, to render uniform, by adjustment of the potential V the distribution on the target of the secondary electrons which fall thereon as has been mentioned hereinabove. Without this ring 34, this distribution is not uniform and varies with the distance from the center of the target. There is thus produced a parasitic charge pattern of potential which when it is swept by the reading beam, becomes visible on a television receiver fed by the output 33, in the form of a spot at the center of the screen. Furthermore, the superposition of this parasitic charge patterns on the charge patterns created by the image, produces a deformation of the output signal, and consequently, a defect in the received image. It is known that the corrector ring eliminates these inconveniences.

It is not necessary that the output signal be taken off on the collector 28 but instead one may also, in contrast thereto, provide in accordance with FIGURE 4, that a resistance 46 is interconnected between the terminal 42 and the ring 27, and that the output signal is taken off at 47 across a condenser 48 connected directly to the target 22.

In addition to the ease indicated hereinabove of transmitting at distance the signal supplied in the electric form at 33 or 47, the tube described hereinabove in accordance with the present invention presents some operational possibilities that are novel and for which there exists a very keen interest.

It will be noted, at first, that the signal may be stored in two elements simultaneously, that is, in the grid 20, on the one hand, and in the target 22, on the other. The signal stored in the grid 20 may be erased by increasing slightly the potential of the grid whereas the signal stored in the target 22 may be erased by sweeping with the readout beam. Consequently, recourse may be had to the first erasing means Without utilizing the second, thereupon receiving a second signal which is, therefore, superposed on the preceding signal in the target, thereupon to read and erase the entirety by the reading beam, or eventually to repeat the process by erasing only the grid 20 to receive a third signal and to superpose the same on the two preceding signals, etc. It is thus possible to obtain at the receiver the image of two or several superposed signals which is extremely useful for the comparative study of recurrent phenomena, for the establishment of correlation, etc.

The present invention is not limited to the illustrated embodiment, but encompasses all different variations of construction and application as known to a person skilled in the art. For example, whereas in the tube of FIG- URE 1 the signal was sequential in time, that is, it Was carried by the electrons of a beam issued by a gun and sweeping the accumulating grid, it is equally possible to apply the present invention to storage signal transforming tubes in which the signal is projected simultaneously on all the points of the storage grid by an electron current issued from a photoelectric cathode. FIGURE 5, limited in its showing only to this modification with respect to FIGURE 1, illustrates an embodiment of such a tube, by utilizing the same reference numerals to designate again analogous parts as in FIGURE 1. The source of signalcarrying electrons is constituted in FIGURE 5 by a photoelectric cathode 49 on which the image is projected across a transparent support 50, and which is carried across the ring 51 at a potential of the order of, for example, 18 kv. The photoelectrons are accelerated by the anode 52, carried across the ring 53, for example, at kv., and pass through the aperture 54 within the electrode 55 to traverse the grid 19 and reach the grid 20, these two grids being analogous to FIGURE 1 and being carried at analogous potentials.

Since, in contrast to the embodiment of FIGURE 1, the axis of the system is occupied in this embodiment by the source of signal electrons, the flooding gun, taking into consideration the necessity to flood uniformly the grid 20, is in this modification of annular shape, as in dicated at 56. The flooding gun is composed of a cathode 57 connected, for example, to ground by the connection 58, of a Wehnelt electrode 59 carried, for example, by

the connection 60 at an adjustable voltage between 0 and v., and of an anode 55, already mentioned and carried by the ring 61 at a potential, for example, be-

tween +50 v. and v. The electrons of the flooding gun pass through suitable slots within the electodes 55 and 59 and are concentrated into an annular beam 62 analogous to the beam 18 of FIGURE 1, and of which the trajectory is controlled by the electrode 17 analogous to FIGURE 1 in such a manner as to flood substantially perpendicularly and uniformly the surface of the grid 20. The remainder of the tube, to the rear of grids 19 and 20 and the target 22 with induced conductivity is substantially identical to that of FIGURE 1, and for that reason has neither been shown nor described herein. Similarly, the operation of this tube is identical to that already described hereinabove, and the advantageous operational possibilities which have also been mentioned hereinabove are equally preserved if, as in the actual case, the signal comes from the transformation of an image which may be projected in visible or infrared or ultra-violet light or in X-rays or gamma-rays according to the case.

Thus, though I have shown and described several embodiments in accordance with the present invention, it is obvious that the same is not limited thereto, but is susceptible of numerous changes and modifications as known to a perosn skilled in the art, and I therefore do not wish to be limited to the details shown and described herein, but intend to cover all such changes and modifications as are encompassed by the scope of the appended claims.

I claim:

1. An electron discharge device comprising:

a target having induced conductivity properties including a metal layer and an insulating :layer of a material providing induced conductivity properties,

two electron sources on the side of said metal layer,

a grid having at least an insulating coating located between said sources and said metal layer,

the first of said sources being provided with means for flooding said grid with a relatively slow and substantially uniform electron beam, and the second of said sources being provided with means for impacting said tg)rid with a relatively fast signal-carrying electron earn,

a ihird electron source on the side of said insulating ayer,

means for sweeping said insulating layer with an electron beam emitted from said third source thereby prcl ducing an output current responsive to said signa and output means for collecting said output current.

2. An electron discharge device comprising:

a target having induced conductivity properties including a metal layer and an insulating layer of a material providing induced conductivity properties,

two electron sources on the side of said metal layer,

a grid having at least an insulating coating located be tween said sources and said metal layer,

the first of said sources being provided with means for flooding said grid with a relatively slow and substantially uniform electron beam, and the second of said sources being an electron gun with means for sweeping said grid with an electron beam emitted from said gun and for impacting said grid with the relatively fast signal-carrying electrons of said beam,

a third electron source on the side of said insulating layer,

means for sweeping said insulating layer with an electron beam emitted from said third source thereby producing an output current responsive to said signal,

and output means for collecting said output current.

3. An electron discharge device comprising:

a target having induced conductivity properties including a metal layer and an insulating layer of a material providing induced conductivity properties,

two electron sources on the side of said metal layer,

a grid having at least an insulating coating located between said sources and said metal layer,

the first of said sources being provided with means for flooding said grid with a relatively slow and substantially uniform electron beam, and the second of said sources including a cathode sensitive to radiant energy and being provided with means for impacting said grid with a relatively fast signal-carrying electron beam,

a third electron source on the side of said insulating layer,

means for sweeping said insulating layer with an electron beam emitted from said third source thereby producing an output current responsive to said signal,

and output means for collecting said output current.

4. An electron discharge device comprising:

a target having induced conductivity properties including a metal layer and an insulating layer of a material providing induced conductivity properties,

two electron sources on the side of said metal layer,

a grid having at least an insulating coating located between said sources and said metal layer,

the first of said sources being an annular electron gun provided with means for flooding said grid with a relatively slow and substantially uniform electron beam, and the second of said sources including a cathode sensitive to radiant energy and being pro vided with means for impacting said grid with a relatively fast signal-carrying electron beam,

a third electron source on the side of said insulating layer,

means for sweeping said insulating layer with an electron beam emitted from said third source thereby producing an output current responsive to said signal,

and output means for collecting said out-put current.

5. An electron discharge device of storage tube type,

comprising:

first storage means for storing electrical signals,

second storage means including a target with induced conductivity properties,

means including a first electron stream for storing electrical signals in said first means,

further means including a second electron stream for transferring the stored signals from said first storage means to said second storage means,

and still further means including a third electron stream for producing electrical output signals from said second storage means corresponding to the firstmentioned stored signals.

6. An electron discharge device comprising:

a target having induced conductivity properties,

two electron sources on the side of said target,

storage means located between said sources and said target,

the first of said sources being provided with means for flooding said grid with a relatively slow electron beam, and the second of said sources being provided with means for bombarding said storage means with a relatively fast signal-carrying electron beam,

a third electron source on the side of said target opposite said second source,

means for sweeping said target with an electron beam emitted from said third source thereby producing an output current responsive to said signal,

and output means for collecting said output current.

7. An electron discharge device of storage tube type,

comprising:

first storage means having induced conductivity properties,

second storage means,

first electron stream means for storing electrical signals in said second storage means,

and means for producing from said first storage means output signals providing, upon visual display, a predetermined brilliance and remanence and containing the information from the electrical signals stored in said second storage means including second electron stream means for producing an electron stream transferring the stored signals from said second to said first storage means and third electron stream means for producing said output signals from said first storage means.

8. An electron discharge device of storage tube type,

' comprising:

first storage means having induced conductivity properties,

second storage means,

first electron stream means for storing electrical signals in said second storage means,

and means for producing from said first storage means output signals providing, upon visual display, a predetermined brilliance and remanence and containing the information from the electrical signals stored in said second storage means including second electron stream means for producing an electron stream transferring the stored signals from said second to said first storage means and third electron stream means for producing said output signals from said first storage means,

and means for selectively erasing energy stored in said first and second storage means.

References Cited by the Examiner UNITED STATES PATENTS 2,748,312 5/1956 Beintema 31512 2,879,442 3/1959 Kompfner et a1. 31512 2,998,541 8/1961 Lempert 31512 FOREIGN PATENTS 990,402 6/ 1951 France, 1,303,223 7/ 1962 France.

709,554 5/ 1954 Great Britain.

930,386 7/ 1963 Great Britain.

OTHER REFERENCES Knoll et al.: Storage Tubes, John Wiley & Sons, Inc., New York, 1952, pp. 47-50, 72-73.

Bruinin-g: Physics and Applications of Secondary Electron Emission, MacMillan Co., New York, 1954, pages 152-153.

DAVID G. REDINBAUGH, Primary Examiner.

J. E. BECK, T. A. GALLAGHER, Assistant Examiners. 

1. AN ELECTRON DISCHARGE DEVICER COMPRISING: A TARGET HAVING INDUCED CONDUCTIVITY PROPERTIES INCLUDING A METAL LAYER AND IN INSULATING LAYER OF A MATERIAL PROVIDING INDUCED CONDUCTIVITY PROPERTIES, TWO ELECTRON SOURCES ON THE SIDE OF SAID METAL LAYER, A GRID HAVING AT LEAST AN INSULATING COATING LOCATED BETWEEN SAID SOURCES AND SAID METAL LAYER, THE FIRST OF SAID SOURCES BEING PROVIDED WITH MEANS FOR FLOODING SAID GRID WITH A RELATIVELY SLOW AND SUBSTANTIALLY UNIFORM ELECTRON BEAM, AND THE SECOND OF SAID SOURCES BEING PROVIDED WITH MEANS FOR IMPACTING SAID GRID WITH A RELATIVELY FAST SIGNAL-CARRYING ELECTRON BEAM, A THIRD ELECTRON SOURCE ON THE SIDE OF SAID INSULATING LAYER, MEANS FOR SWEEPING SAID INSULATING LAYER WITH AN ELECTRON BEAM EMITTING FROM SAID THIRD SOURCE THEREBY PRODUCING AN OUTPUT CURRENT RESPONSIVE TO SAID SIGNAL, AND OUTPUT MEANS FOR COLLECTING SAID OUTPUT CURRENT. 